No one can claim to be blindsided by director Cassie Jaye’s staunch advocacy of same-sex marriage. It’s in her documentary’s title: “The Right To Love: An American Family.”

The film mostly revolves around the acrimonious debate about California’s Proposition 8, which sought to overturn a court ruling that legalized gay marriage. (The ballot initiative was approved in 2008.) The title family consists of the exceedingly personable Jay and Bryan Leffew and their two charming adopted children. The two men’s smart, earnest observations are set against montages of anti-gay advertisements, wherein households like theirs are described as harbingers of America’s collapse.

The wholesome normality of the couple strengthens Jaye’s argument, but weakens the movie’s dramatic tension. Some of the carefully selected anti-gay figures already resemble historical artifacts; clips of Ann Coulter and Kirk Cameron make them both look about as relevant as a couple of “Impeach Clinton” buttons. Jaye does, however, have the evenhandedness to include Joe Biden flatly rejecting gay marriage, on behalf of both himself and Obama, during the 2008 campaign.

The film is unlikely to bring about any debate since the likely audience for Jaye’s film is already convinced.